151.翻转字符串里的单词
双指针
class Solution {
public String reverseWords(String s) {
StringBuilder sb=removeBlank(s);
reverseAllWords(sb);
reverseEachWords(sb);
return sb.toString();
}
public StringBuilder removeBlank(String s){
StringBuilder sb=new StringBuilder();
int leftindex=0;
int rightindex=s.length()-1;
while(s.charAt(leftindex)==' '){
leftindex++;
}
while(s.charAt(rightindex)==' '){
rightindex--;
}
for(int i=leftindex;i<=rightindex;i++){
if(s.charAt(i)!=' '||sb.charAt(sb.length()-1)!=' '){
sb.append(s.charAt(i));
}
}
return sb;
}
public void reverseAllWords(StringBuilder sb){
int leftindex=0;
int rightindex=sb.length()-1;
while(leftindex<rightindex){
char temp=sb.charAt(leftindex);
sb.setCharAt(leftindex,sb.charAt(rightindex));
sb.setCharAt(rightindex,temp);
leftindex++;
rightindex--;
}
}
public void reverseEachWords(StringBuilder sb){
int leftindex=0;
int rightindex=0;
for(int i=rightindex;i<sb.length();i++){
if(sb.charAt(i)==' '){
int start=leftindex;
int end=i-1;
while(start<end){
char temp=sb.charAt(start);
sb.setCharAt(start,sb.charAt(end));
sb.setCharAt(end,temp);
start++;
end--;
}
leftindex=i+1;
}
if(i==sb.length()-1){
int start=leftindex;
int end=i;
while(start<end){
char temp=sb.charAt(start);
sb.setCharAt(start,sb.charAt(end));
sb.setCharAt(end,temp);
start++;
end--;
}
}
}
}
}
卡码网:55. 右旋字符串
双指针
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int n = Integer.parseInt(in.nextLine());
String s = in.nextLine();
int len = s.length(); //获取字符串长度
char[] chars = s.toCharArray();
reverseString(chars, 0, len - 1); //反转整个字符串
reverseString(chars, 0, n - 1); //反转前一段字符串,此时的字符串首尾尾是0,n - 1
reverseString(chars, n, len - 1); //反转后一段字符串,此时的字符串首尾尾是n,len - 1
System.out.println(chars);
}
public static void reverseString(char[] ch, int start, int end) {
//异或法反转字符串,参照题目 344.反转字符串的解释
while (start < end) {
ch[start] ^= ch[end];
ch[end] ^= ch[start];
ch[start] ^= ch[end];
start++;
end--;
}
}
}